High frequency amplifier and circuit therefor



June 7, 1938. A. zlLLG-.ER 2,120,122?

HIGH FREQUENCYAMPLIFIER AND GIRGUlT THEREFOR Filed sept..15, 195s 5 sheefs-sheet 1 Iune 7, 1938. A. zlLLGER 2,120,122

HIGH FREQUENCY AMPLIFIER AND 4CIRCU'.' THEREFOR Filed sept. 13, 1935 5 sheets-sheet v2 WM NQ U m l E K 1 V u m H/N O w Wb\ H VI B M E M n.2 u A D# M n M NQ wS QQ RVA WS N NN mi K W no W s m Hm, mmlm +B .n.5

June 7, 1938. A. Z|LLGER 2,120,122.

` HIGH FREQUENCY AMPLIFIER YAND CIRCUIT THEREFOR Filed Sept. 13, 1933 5 Sheets-Sheet 3 l M am ,L .2W

4 A'r-roRNEY June 7, 1938. A. zml- GER I HIGH FREQUENCY AMPLIFIER AND CIRCUIT THEREFOR vFiled sept. 1s, 1933 5 Sheets-Shed 4 23W, 552 0 a 7.6 l 5,

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Z I W v INVENTOR HRA/o Z/MGE/ A'ITORNEY June 7, 1938. A, Z|L| GER 2,120,122

HIGH FREQUENCY AMPLIFIER AND CIRCUIT THEREFOR Filed Sept. 15, 1935' 5 Sheets-Sheet 5 INVENTOR /Zwvo Z/MGFR ATTORNEY Patented June 7, 1938 o-Nrrso simrss oFF-1c HIGH'" FREQUENCY* Alvrenmmm c1151- CUIT-THEREFOR- Arno Zi'llger, Narbertli,

TelvisionrCorpo'ration, Wilmington; Deli, a Y corporationof Delaware` Applicatonseptemb'er 13, 1933,*Seral'fNo;` 6895256 D they. are strong enough to broadcast over the-air or tofsend over wires to there'ceivin'g apparatus.'

The receivingV4 apparatus picks upl the 'impulsesV thus sent out andV again amplies'fth'em: sufciently'to operate :l1/modulating lamp, the" light f-.,t-of fwhich is caused by a suitable scanning deviceY to illuminate successive points of the received picture image. 4 y y In order to produce a picture with fair detail relativelyhigh frequencies are" necessary.A Thus g01af-picture'having 60 linesWithWZpicture elements on a line and transmitted at the rateof' 20 picturesper secondhas 86,400 picture eleL ments'per'second' and the signal may have a possible frequency of43,200"cycles`per second.

g Where a greater'number ofv lines is used in 'the' picture, andfa greater numberof picture elements per line; and aj greater' number of I pictures Y per second, the frequency may rise to a much'greater gure than this; perhaps, in .theneighborhood `of ;-.n'200,000'cyc1es per second; The' averagerafdioA receiverffor -sound reproduction amplies a fre; quency in the neighborhood of 10,000-cycles`per second and cannotgo muchhigherl4 This'frequency appears to bel sufcient in the audible' 3,-, range'and hence there has been littleefi'ort made to design amplifiers' for4 the "higher frequencies By means of resistance coupled anripliers' a higher frequency can be had but thereis usually a distortion caused Abyfunequalpassing of7 high?l i and low frequencies with highimp'edance' in' the" output circuit preventing the'transmission'of the' impulses over -wires for any appreciable distance.

Transformer coupled amplifiers have heretofore' completely cut 'off-the high frequencies? above say .15, 10,000 cyc1es,=and havea tendency to pass cer tain frequencies better' than others.-

Itis one of the' objects of the present inventionA to provide an amplifiery which will pass without distortion frequenciesin the neighborhood lof^ (3 200,000 cycles or higher.l

Another object of the invention is-to provide f an amplier for high frequencyoscillationwhich' has a lowl output impedance so that' signals -frorn v the amplifier may-be -sent"relatively longdistance 55 over-Wires# l Still' ano'thefobject* of the invention'his the` provision of a high frequency-amplier in which the high potential" circuits andI thosev which are' highlyf'se'nsitivearefseparated fromthe 1oW` poL tential* 'circuits and` capacity between'V them is reduced to a minimum.

Another-2 object of the invention is to' provide an amplifier tube'linwhich the input capacityV is reduced to a` mihimumfas'we'll' as'the grid-plate capacity;

A stillA further' 'object ofzthei invention is fto provida pushf-pull amplifier-'tube for vvuse'with'high frequency icircuits inwhich the capacities` be`` tween the gridsfand platesand between the' grids and cathodesare reduced`v to" a minimum.

Still another objectfoffthe invention is to lpro`v videfameans for mounting'fstandard tubes ins high frequencyv amplifier" so"4 as to' maintain:v at

grids, plates,V and*- catho'des ofthe tubes.

Av still'ffurtherobject of the invention' isto` provide a'v high I'power'v output' tube fora highr frequencyl amplifier `with; minmum capacity bei' structions i of -"Va"riou's partsffor? carrying' out 'the' purposes fof"the"inventin' 'Will beappareiit asthe description thereofk proceeds.v

The inventirhasben "ill ytratel in'y theac'- companying drawings in' which: i'

Fig.'- 1 is a* partly 'cliagair'nmatic perspective viewof fanfamp-lir constructed in accordance withA my-imprvedfdesigii Fig'. 3 is afcircuit diagram'of a'mdifedform In.iulaltinglarlpj?r l l Fig. 4 is a perspectiveview rpartly'in sectionof used With'theamplierof the inventiori;`

IFig. 6 isajsectional sidev 'elevatiral elements shown inl-Fig.l 5; j 'Y Fig is aplair Viewy of the'elements shown in Fig; 6; Y

Fig; 8 is 4Wa sectionalplanfviewtaken ronl the lamp.l showing a "modified filament construction;

a mnimumfthe capacitive effect between the' Otherfobj'ects and obj etats"relatingto'particular Fi'g. 5 'isal sectional 'frohtel'e'vational View of one forni f'ofpower"`outpiit tubewlich Vmaybe View ofthev a special type of amplifier tube which Vmaybel -ing a separate and distinct level for all of the high potential circuits in the amplier and another level for the lowY potential circuits, and providing certain specially constructed tubes and other parts which will be hereinafter described.

In Fig. 1 is kshown an amplifier having two stages of so-called radio frequency amplification, a detector stage, and three stages of transformer coupled amplification. The circuit comprises an antenna coil I having a primary coil 2 one end of which is connected to the antenna 3 while the other is connected to ground at 4. The coil I has aYY secondary Winding 5 which is connected at one end to one side of a variable condenser 6 and tothe grid post 1 of a special amplifying tube 8, Ywhile the other end of the coil is connected tojthe rotor of the condenser Y 6 and to ground at 9.

The tube 8 has a grid p-ost 1 mounted on the glass bulb at the top, as indicated, and at the opposite side of the bulb is provided a plate conjnecting post I Il mounted in a similar manner.

The base I I of the tube is' provided with theusual terminalsso that. it ts into afstan'dard socket I2 having two heater terminalsI3, a cathode terminal I4andva screen gridI terminal I5. The

cathode terminal I4 is connected through a resistance I6l which has aby-passjcondenser I1 to a ground Wire I8 grounded at I9. 'Ihisimaintains the cathode at a Vhigher potential than ground and is done to give the grida negative bias, as is 'well known. 'I'he resistance I6 may be made variable as one means of controlling the volume of the amplifier. Any other type of volume control lmay of course be used. The heater terminals I3 are connected by means of a -twisted pair of wires 20 which lead to a secondary 2I on a transformer 22 the primary 23 of which is connected to thealternating power line as indicated by the generator 24. `The secondary 2| has itsV midpoint grounded as at 2Ia. The screen grid terminal I5 is connected toa. wire 25 which is given a positive potential at 25a. A bypass condenser V213 is connected between the terminal I5 and aground connection at 21, the condenser being positioned -in close proximity to the screen grid connection. The plate terminal I9 of the tube is connected to the primary winding 28 ofthe coil 29 which has its other end connected by means of the wire.Y 30 to the positive side of a B battery (not shown but designated,V

B-}-) `or to any'eothersource of platepotential supply@ i Y The coil 29V has a secondary winding 3I; one'Y end of .which is yconnected to the Variable .condenser 32 and to the grid post V33 of the second amplifier tube 34, while the other endis con-V nected to the. rotorof the condenser 32 and to the grounded wire I 8 byY means of the wire 35. The tube 34 is similar to the tube B 'and isf mounted on asimilar socket 36 which `has a cathode terminal 31 connected through a resist-' ance 38 and by-pass condenser 39 to the grounded wire I8. The heater terminals 40 o-n the socket 36 are connected by means of the Ytwisted wires' 4Iv to the heater supply secondary 2| of the transformer 22.'v The screen grid connectionj is connected to the wire 25 which provides the potential of the screen grid as described in connection with the last tube. A condenser 2lia is placed in close proximity to the screen grid connection 42 and is connected to it and to ground-at 21a.

While the twisted wires for the heater supply have been shown rather long on the tubes 8 and 34 and also on the succeeding tubes, it will be understood that this has been donerforpurposes of illustration `only and that these connections are actually made as short as v'possible to reduce any Ytendency to pick up the sixty cycle hum by the other wires of the circuit.

The tube 34Y has a plate terminal 43mounted on the bulb similar to the plate terminal I0 of the tube 8, and this terminal is connected to a primary winding 44 of the coil 45. The other end of the winding is connected by means ofthe wire 46 to the plate potential supply as indicated by B+." IThe coil 45 is provided "with a secondary 41fwhich has one end' connected to'` the VVariable condenser 48 andV also throughL a` grid leak and condenser 49 to the grid terminal 5I] ofthe detector tube 5I. 'Ihe Vother end of the secondary 41 is connected to the rotor of the condenser 48 'and by means of the wire 52 to the ground wire I 8.

The special detector tube 5I is mounted upon.

a standard'base 53 having a cathode connection 54 and twovheater connectors 55. The'cathode connector 54 is connected directly to the grounded wire I8 by meansof the wire 56. The terminals 55 for the heater are shown connected by means of the twisted Wires 51 tothe heater supply transformer `22 as indicated. i

The detector tube 5I feeds into a transformer,

58 which is specially wound to pass high frequencies. This transformer forms no partof the present invention but has been 'developed by Wired Radio Inc., 'of Ampere, New Jersey. 'I'he detector tube 5I has a plate terminal 59 mounted on the bulb similar to the tubes 8 and 34 which connects by means of a wire 60 to a terminal 6I on the top ofV the Vtransformer which is connected to one Vend of the primary coil (not shown). v has a terminal 62 arranged at the lower end of the transformerand this terminal is connectedV through a balancing resistance 63 by means of cated at B+. e

The transformer 58'to be described is the first of a series' of push-pull transformers and the secondary of this transformer has a midpoint connection brought out at the terminal 65 at the4 lower end thereof which .71's connected by means' of the wire 66gto the common ground Wire I8.

The two rends of the secondary' of the trans-y former 58 are. provided withterminals 61 and 68 Y atthe top of the transformer and these are con-l nected respectively by means of short wires-,69

and 1I) tothe grid terminals 1I and 12 of thel special push-pull amplifying tube 13 which is to be hereinafter more specically described.

The tube 13 is mounted on a base 14 which fits into a standard socket 15 having at least three terminals, a cathode terminal 16 and two heater The other end, of the primary' coil .50 the wire 64 to a positive plate potential as inditerminals 11'.y The cathode terminal 16 may bev v connected through a resistance and Icy-pass condenser 18 to the grounded wire I8. `The two heater leads 11 vare connected by twisted vwires 19 to the power supply circuit at the transformer secondary 2AI. The push-pull tube 13 is provided with two plate connectors V8Il'and 8I which mayY be. connected by meanszof .wires 82 andA v0311espectivelyY to plate Vterminals 84= and 85 ons the second push-pull transformer 88.

connected to the ends of the primary coillithereof which in turn has a midpoint connection provided with a terminal 81 at the lower end of the transformer which may be connectedby means of the wire 88 to a platepotential indicatedatV The transformer 86 is provided with a secondary coil havingend terminals 89"andr901fat` the tcp thereof which may befconnectedy respectively by short wires 90% and 9| tothe grid terminals 92vand 93 of the second push-pull amplifyingtubel 94 which is made exactly similar tothe rst tube. The midpoint of the secondary of the transformer' 85fis brought out-through aiterrninal89a and connected directly to the grounded'wire |8. The tube 94 is provided with a socket 95T having heater leadsI 96' connected by means of the twistedwire 91 to the power supply and a cathode terminal 98 connected through a resistance 99 and by-pass condenser to thegrounded wire |8.--

Two plate terminals |00and |0| are providedon the top of the tuber 94. These may be con.- nected respectively by means of wires |02 and |03 to the primary end terminals |04 and'lii'V on the top of the push-pull transformer |06.

The midpoint terminal |01 Yof thisl primary' is provided at the bottom of the-transformer and may be connected by means of the wire |08to a plate potential indicated by B+. The transformer |06` is also provided with a secondary having endy terminals |09 and ||0 which may be- H8 to the secondary ||9 ofthe transformer- 22 for giving the tube- ||5, which corresponds-to the 45 type tube, a different filament Voltage than the preceding tubes. The-secondary ||9 may have its center point connected-Ytoground at- |20 through a resistance |2'| provided withv a by-pass condenser |22. This maintains the filacent of the tube ||5 at a higher potential than' ground thus properly biasing Ythe grid.

The output tube V| I5 is provided with two plate terminals |23 and |24'whichmay be connected by means of the leads |25 and |25 to a coupling transformer |21.

cated at B+. The ends of the secondary of the transformer |21 `'are provided withterminals |32 and |33 which may be connected `respectively bywires |344 and |35 to a neon glow lamp. |36 theplate of which may be scanned by suitable means for producing a television picture in accordance with the incoming impulses of the ampliieru Grid leak and condenserA rectification has been shown for purposes of illustrationin connection with this circuit but yit'willbe-understood-that` Theseftermif' nals. are at the top .ofthe transformerA and are- Hence Y no cathode terminal-- need be providedV on the socket |I6 for the tube but heater terminals |1 are provided which maylv beindependently connected by the twisted wires-V This transformerl has a pairA of primary terminals |28 and |29 to which are connected the leads |25 and |26,`and the mid-l point of the primary is brought out-vthroughaV terminal |30 which may be connected by-means Y of a wire |3|`to a positive plate potential indi-V if desired'.

InFig.. 2 is sh'own the circuit diagram corresponding to the amplifier ofFig. 1 fronrsthedeetector tube 5| on. Here the tubes 13, 94; and

||5 areV indicated as containing two. separateA sets'V Thus the tube 13`has` two grids'. |31 and |38:connected tothe grid terminals '1| and: 12-respectively on the outsidel of `thefbulb, twoY of elements.

plates |39'and |40 connectedrespectively tothe external plate terminals Bil-'and' 8| on the cuteV side ofthe tube, two cathodes |4| and |421 con,-`

nected together inside of the tube.and. to'xthe. externallcathode terminal 16; and a pair offheatfv ers |4'3-'and |44 connected in parallel andtolthe heater terminals 11.

The tube 94 is exactly similarY to thetubef13' andV need not be further described in connection with this-figure.

The tube ||5 is a power output tube with-twoV sets ofvelements. Thusa pair of grids |45and |45' are connected respectively to the external grid terminals ||3 and ||4, whilevthe anodes |41 and |48 are connected to the external plate terminals |23 and |24respectively. Between the ridV |45 and plate |41 is the filament |49,-\while1 the filament |50 is between'the Vgrid-7|4i-'and the plateI |48. These filaments are connected in parallel to theiilament terminals I1 at thebase of the tube.

From this construction as illustrated in these two figures it will be evident` that a push-pull circuit is provided in which the usual two amplifying tubes for amplifying each side of the circuit in one stage are included in one envelope,V thusfacilitating the construction of the ampliiierand-f the positioning of the unit so as to keep thehigl potential circuit separated from the -low potential circuit. The manner 'of constructing these tubes will be'more specifically described later.

Attention is drawn to the resistance 63 in vseries with theprimary of the transformer '53.:Y This resistanceis inserted to balance the-impedance between the plate and cathode of the detector tube so that the high frequency side of the transformer is balanced with thelowfrequencyside thus preventing distortion inthe high frequency current. forms no part of the present invention but is described and claimed in my prior filed application Serial No. 682,209, filed July 26, 1933, entitled Balanced amplifier circuit.

other types zma'y be usedsuchasplata rectifica--v tion.. Alsov othersgridrbiasing .means maybe used The placing of this resistanceV The amplifier as described above may be usedl with a plate type neon lamp as indicated at |36 but I may prefer to use a different type-ofv lamp having a much higher current consump tion. Such a lamp, illustrated in Fig; 3 is shown and described in Patent` No. 2,089,806 toV JohnI W; McKay. Such a lamp is constructed of two bulbs |5| and |52 spaced apart'fr'om-each other and connected by a glass tube 58. |52 contains the anodeand the' bulb |51 con'-l tains the cathode; and a terminal |54 ismounted on the bulb E52' for the anode while a4 terminal |55 on the bulb |5| is connected to thel cathode.V

In order to operate such a lamp itfmay Vbe necessary to use several output tubes --in'par-f allel. In one instance i found itfnecessary to use three of the 45 type tubesfin parallel, butconnecting these tubes in the ordinary mannerinecessitates a` number of lwires `between 'the grid connections andl between theplate connections#- which cause consider-able capacity-'not'- onlyffben AAL twee'n themlbutV to ground` and tothe lament leads. A feature ofthe invention, therefore, is

the overcoming of this defect by the construc.V

tion of atube which contains all of the` output 1 tubes necessary inlone envelope.

This tube is shown diagrammatically in 3 Where the yenvelope `|59 contains the three sets of'filaments |51, |58, and. |59, the three plates |60, 6|, andY |62 connected together, andthe three grids |63, |64, andV |65 also connected together. The grid and plate leadsvare so con-Y structed. asv to minimize Vthe capacity effect as Y willbe described later, it being sucient to point outat this time that the grids are connected bymeans of a wire |66 to the grid terminal |09 ofthe transformen |06 while the other end ||0 of the secondary of the transformer isV connected toground by means of the wire |01. yThe midpoint of the secondary |09in Fig. 2 isnot used in this case. VThe plates of the tube are connectedby means of a WirelES to thev cathode `terminal |55 ofthe lamp while the anode ter. minal |54 Vthereof is connected to a positive povIn Fig. '4I Vhave shownone type of amplier tube ,which may be used for the radio frequency,

' carries the various terminals for making the base |10.l The other two prongs on the base (if Y connections to the tube.

vsupport rods |13.

rods |13.

The tube is provided with an internally extending press |1| which has integrally formed upstanding glass legs |12 on the ends thereof in which are sealedthe plate Upon these support rods is mounted the whole element assembly.

VFor, such a mounting the anode is constructed of 4a pair of `metal plates |14 stamped out with a-semi-cylindrical portion |15 extending through the center thereof.. These plates are attached togetherin such a manner that the semi-cylin- .drical'portions |15 form acylindrical plate or anode, and suitable curved portions |16 at the edges of the plates fit over the plate support At each end of the anode construction is placed a mica plate |11 with. holes |18 to receive the anode support rods, a central hole |19 to receive the tubular cathode |879, and on either side of the hole |19 another hole |8| to receive the grid posts |82. Thus the grid and cathode are supported with respect to the anode.

An insulated lamentary heater wire |83 eX- tends in the form of a loop or hairpin through the tubular cathode and has its ends attached to the support rods |84 inthe press |1|. Lead-in Vwires |85 connect the lament support rods withV the two heater prongs |86 on the base |10. The tubular `cathode may be held longitudinally in place by a strip |81 which surrounds the lower end thereof and this strip may be welded to a support rod |38 sealed in the center of` thepress |1|. A lead-in wire |89 from the rod |88`Ymay be connected to the cathode prong |90 onthe it,V is to t intoa standard five prong socket) are not used. 1

One of the plate support rods |13 at theV top is connected by means of a wire |9| to a metal cap |92 attached to the outside of the bulb at one side of the top thereof, the wire being fused or sealed through an opening in the glass in the manner of making the grid connection,Y on a shield grid tube.

of the wire |93 to acap |94 mounted on the opposite side of the top of the bulb.V The wires |9| and. |93 are given a slight sinuous curve inV order to permit small movements of the element. structure withinV the bulb due to temperature In y'like manner one of 'thei grid support rods |82 may beconnected by means changes and thus to eliminate any strain on ther vand grid connections are separated from eachother and from the other parts of the tube, especially the low potential circuits.

While this tube is shown as a Vsimple 56 type it Will be evident that a shield'grid tube maybe manufactured in the lsame manner, there being required an additional leadk down to oneof the base rprongs for the shield grid potential connecetion. Such a tube with a shield grid is shown as vtubes 8 and 34 in Fig. 1, while the detector tube 5| of that figure maybe constructed exactly similarto the tube shown in Fig. 4'. It will be noted that the plate and grid connections through the press downtothe base of the tube are entirely eliminated which removes a large part offtheV undesirable capacity between theserconnections in the ordinary tube.

In Fig. 10 is shown a. tube siniilart that in Fig. f 4 but provided with tworsets of elements makingV it a push-pull tube similar to the tubes 13 and 94 of Fig. l. In this construction the envelope |95 is supportedupon a base |96 carrying aplurality of terminals for making the connections to the tube. kAn inturned press|91 supports theele-` ments and for this purpose is provided with up-l standing end p osts |98 similar to those shown in the tube of Fig; 4. A pair of support rods |99l are fused intov the glass posts |98 and to these are 'fused on each side artransverse glass bead, 2,00.- Into these glass beads are fused the plate. support rods 20| and 202 of a pairV of element assem- Y blies 203 and 204 which are exactly likethe element assembly shown in Fig. 4 and need no spe- Vcilc description here.

The two cathodes 205 and 206, shown best in Fig. 12, are vfastened together by the metal strip 201 which is welded to the central support rod 208. port rod and leads to the prong 2|0at the base of the tube. The filaments are connected in parallel and forthis purpose the end 209 of one filament is connected to a transverse connector 2|0 as is also the end 2|| of the other lament.

`The connector 2|0 is attached to a support rod 2 2 which is sealed in the pressV |91. In like man- Vner the ends 2|3 and 2|4 of the lament are `secured to the connector 2|5 which in turn is attached to the support rod 2|6 sealed in the press |91. Lead-.in wires 2|1 and 2| 8 may conneet the heater rods 2| 2 and 2|6 respectively with heater prongs 2|9 .and 220 as indicated.

One of the plate support rods 20| is then connected by means of a wire 22| to a cap 222 on the outside surface of the bulb while one of the other plate support rods 202 is connected by means of a wirev2r23 to a cap 224 also positioned on the outer surface of the bulb atabout 45 degrees re moved from the other. In the same manner the grid post 225 on the element assembly 203 may be connected by means of a wire 226 to the cap 221 on the outer surface ofthe bulb about diametri:

A lead-in wire 209 is connected tothis sup--V cally opposite the plate cap 224 andthe grid post 228 of the element assembly 204 may be connected by means of a wire 229 to the cap 230 on the outer surface of the bulb about diametrically opposite to the cap 222.

The tube, of course, is prepared and treated similarly to ordinary vacuum tubes .of this nature and may be provided with a getter cup 23| suitably supported by means vof the wire 232 on one of the support rods, as for instance, the rod |99.

It will be evident from this construction that the two element groups 203 and 204 are independently positioned in the envelope so that each operates separately as far as the plates and grids are concerned and can therefore be used in pushpull formation. As the cathodes in a push-pull circuit are connected together this connection is made in the tube and therefore avoids the additional wires and their accompanying capacity eiect. As in the other tube previously described the grid and plate supports are entirely separated from the other wiring, especially from Vthe wires which usually pass through the press of the tube and the capacity effect caused by Such wiring is thus eliminated.

The power output tube H5 of Fig. 1 may be similarly constructed although instead of a separately heated cathode a ilamentary cathode may be used. In this case only the heater terminals on the base of the tubes are used while other parts of the wiring would be the same.

In Figs. 5 to 9 inclusive is shown a tube corresponding to .the triple element output tube indicated diagrammatically in Fig. 3. This tube has the same characteristics as three 45 type tubes connected in parallel but a large amount of the disadvantages arising from such a hook-up is eliminated. This tube comprises an envelope 233 supported on a base 234 in the usual manner and having an inturned press 235 for supporting the elements. The elements of the tube comprise three independent element assemblies 236, 231, and 238. These element assemblies are exactly the same and it will be deemed therefore only necessary to describe one. The assembly 236 comprises an anode or plate 239 having two lcomplementary parts which when positioned together provide a tubular central portion 240 having substantially rectangular cross-section and two side extending anges 24! which may be attached to side supporting rods 242. A grid 243 composed of a helix of wire is wound about two support rods 244 which are longer than the plate and extend above and below it. A single sheet of mica 245 is provided across the top ofthe three element assemblies and a second single sheet 246 of the same material is provided across the bottom. The plate support rods 242 pass through holes provided for them in the mica sheets which tend to rigidly support the element assemblies in spaced relation within the envelope. Also the mica sheets are provided with holes to receive the grid support rods 244 thus maintaining the grids in spaced relation to the anodes.

The element assemblies are mounted inside of the envelope 233 by means of two glass extension supports 241 formed on the press 235. The ends of these glass extensions are bent outwardly and are provided with short rods 248 sealed therein.

The plate support rods 242 of the central element assembly are made somewhat` longer at the lower end and are welded to the rods 248 thus supporting the whole assembly within the envelope. Transverse rods 249 mounted directly under the Y anodes.

anodes are welded to each of the rods 242, th making .an .electrical connection betweenthe three A fllamentary cathode 250 comprises an M.- shaped filament which is supported within the grid 243. The two upper vertexes 4of the lament are supported on springs-25l which in turn are held by a small glass tube 252 whose lends are supported by short support rods 253 inserted in the ends of the tube and welded to the upper ends of Vthe plate support rods 242. In order to support the lower ends of the filament a glass bead is provided in which two rods 254 and 255 are sealed. These rods extend both above and below the beads and have their upper ends -connected yto the ends of the filament. support rod 256 is sealed in the center of the beadand its upper end terminates in a hook 251 which holds the central V-shaped loop of the M filament. In order to support this glass bead I provide a short support rod 258 in each end of the bead and these rods are then welded lto the plate support rods 242 thus rigidly mount- -ing the bead beneath the plate.

One of these beads is mounted beneath'each element assembly. A transverse connecting Vrod 259 is connected to the lower end'of each of the rods 254 passing through the three beads, and a second transverse connecting rod 260-is welded to the lower ends of the three rods^255 passing through the three beads. Thus Vthe three i'llaments are connected lin parallel. In order to make the outside connection for the filament I connect the central support rods 254 and 255 to two short support rods 26| and 262 respectively, these support rods beingy sealed in the press 235 and having lead-in wires 263 and 264 connecting them respectively with heater prongs 265 and 266 at the base of the tube.

As the anodes or plates are all connected together by means of the rods 249 it is necessary only to connect one of the support rods 242, as by means of the wire 261, at the top thereof to a plate terminal 268 mounted like a cap on the outside of the envelope near the top thereof. The grids may all be connected together by means of a transverse rod 269 which may be welded to the upper ends of the grid support rods 244 and this rod may be connected by means of a wire 210 to a grid cap 2-1l mounted on the outside of the bulb, preferably diametrically opposite the plate terminal 266. The wires 261 and 210 are given a slightly sinuous curve to allow for movement of the elements due to expansion Vand contraction and to remove any undue strain on the seals where vthe wires pass through the glass envelope which they necessarily have to do. The mica sheets 245 and 246 are each provided with openings 212, 213, and 214 to permit the mounting of the filaments without interference.

The M filaments 250 shown in Figs. 5, 6,V and '7 are connected together at their ends thereof, the vertexes being insulated from each other. Inasmuch, however, as these filaments are con- .nected in parallel it is possible to connect the vertexes together without insulating them and this simplifies the supporting structure. In Fig. 9 this way of mounting the filaments is shown. The filaments 250a have one end connected to the transverse conducting member 259a while the other ends are connected to the transverse conductor 2603. The conductors 250a and 2611a are connected respectively to support rods 26|a and 2625 which are sealed in the press 2352*. The lower vertexes of the filaments are supported'on ihooks, V'1a which are in turn 4Welded to a transV -verse connectorv 256aA which is supportedupon a central support rod 258a also sealed'in'the press. .'Ivhegright hand upper Vertexes of the three filamentsiseen" in Fig. 9 Yare supported on springs .-2,5lasuspended fromja rod 252a having its ends sealed in separated glass beads 253e. A second ,support rod 254a is mounted between thebeads the other three-quarters' of the filament, and that n element assembly would knot be completely incapacitated.

yFrom the above description it Will be evident that-the three element assemblies 236, 231 and 238 are connected in parallel, the plates being connected together, the gridsbeing connected to- .gether, and the filaments being connected together. These connections, however, are made inthe tube With a minimum of Wiring so that theY capacity kbetween various yelements is reduced to an absolute minimum. f

The above description has been directed to an amplifier for high .frequency oscillations in which specially designed tubes `have been used. It is evident, however, that it is possible to use standard tubes in a high frequency circuit by following as nearly as possible the principles already outlined, although naturally the results will not be asV good.

While the `inventionhas been described with a certain type of amplifier and using certain types of tubes the invention may be adapted to any system of amplification Which Will be greatly improved for high frequencies by maintaining the high potential and highly sensitive circuits on one level and the low potential circuits on another. Also the special tubes described are not to be limited to any particular type as any tube from triodes up to the more complicated pentodes may be adapted for this type of circuit With equally good results. I do not, therefore, desire to limit any part of the invention kto what is shown and described except as such limitations are contained in the appended claims. l

What Iy desire to secure and claim by Letters Patent is: Y'

1. A high frequency amplifier' comprising a plurality of amplifier tubes coupled together by transformers, terminals for the grid and plate connections at spaced points on the tops of said tubes, grid and plate terminals on said transterminals whereby the length of theY connection from the grids and plates'of the tubes to the.

."formers, and'meansto position said.transformers n' 'with respect to said tubes so that said terminals ,Y are at substantially the same level'as the, .tube

having a press, a grid, a. plate spaced from said grid, a cathode spaced from said grid, means to support said plate, grid', and cathode ons-aid Y press, connections for.- said cathode [extending through said press, a connector-for ysaid grid mounted on the top of said envelope, a connector for saidjplatemounted on Vthe top vof ksaidenvelope and spaced from ,said grid connector, la

plurality oftransformers capable of passing `high frequencies, said transformers having grid connectors and plate connectors, and means to mount said transformers in'olose proximity to said tubes With said plate connectorsV and` said grid con,-

nectors about approximately Vthersame level as said'plate and grid connectors on said tubes: v3. An amplifier for high frequency oscillations comprising aplurality of amplifying tubes, each of said tubes having grid and plate Vterminals provided at one end of the tube spaced from` the otherterminals for said tube, coupling units between said/tubes', said coupling units being sub'- stantially as large as the tubes and uhaving the terminals for the plate terminal of one tube 'and the 'grid terminal of the next positioned at one end of the unit While the other terminals are positioned at the opposite end'of the unit,V and means to position said tubes and coupling units so that the connections between the grid and plate terminals of saidtubes and said units are maintained vsubstantially at the level ofthe top of said tubes.`

' 4. A high' frequency*amplifier comprising a plurality of amplifying tubes each of said tubes having a press,a grid, a plate spaced from said grid, a cathode spaced` from said gridmeans to supportsaid plate, grid and cathode on said press, connections for said cathode extendingY through said press, a connector Yfor said gridI mounted on the top of said envelope, a.v connector for said plate mounted on the top of said envelope and spaced from said grid connectona plurality of coupling devices capable of passing high frequencies, said devices having Vgrid con- Ynectorsand plate connectors, and means to mount said devices inclose proximityto said tubes withY said plate connectors and said grid connectors substantially at the same level as said grid and plate connectors on said tubes.

Y ARNO ZILLGER. 

